After a long time of this not being an active project (I got a fun bit of commercial work that absorbed my time, and taught me lots about PRJC's Teensy 3.1! But for another project...) I was reminded of this by being given a "skull" by jlbrian7.
As it happens, I've recently ordered a bunch of ESP8266 dev kit (a nodeMcu board, and a couple of bare ESP-12E's), and had a hankering for more PCB design, so finishing this project seems like a natural choice.
One of the things which I picked up on earlier was the fact that the RJ11's in the middle couldn't be the same through hole components used on the original board, as the pads would get in the way of the ESP module sitting flat against the board. Fortunately, with a bit of parametric searching on Farnell, I've found some Molex RJ11 connectors that have both surface mount contacts AND mounting points, so they won't poke through to the other side of the board and interfere with the module.
Flat as a pancake
And they're not hideously expensive either at £0.775 on the UK Farnell site at the moment (Order code 1471565). The body of the connector is 18mm long, which, with the contacts, might make it a bit of a squeeze. But it should fit. True, I won't get the same mechanical strength I would with through-hole mounting posts, but these are for internal connections that will only be mated once or twice (I hope!) and won't have any oafish users (like me) plugging heavy cables in from the outside and pushing them about on a frequent basis.
The RJ45 and DC jack, on the other hand, are the vertical type, and I won't bother with surface mount as it'll simply take up more board space than it needs to (the contacts will have to point away from the connector, rather than straight down through the board). Also I'd like to retain the mechanical strength afforded by fixing them through the board, as this connector will be accessible from the big scary outside world, where there are ogres with TTL to USB cables and DC wallwarts who want to break my connectors.